1. Field of the Invention
This invention relates to posts or pilings and protective end caps.
2. Prior Art
Wooden posts and pilings deteriorate in use from exposure to weather, bacteria, fungii and insects. A primary cause of this deterioration is the entry of moisture at end surfaces of the post or piling, due to the exposed end grain. Moisture is carried into the post by capillary attraction and may cause the wood to rot or may become frozen and expand to cause cracks and structural defects that shorten the useful life of the post. This deterioration requires the replacement of posts or pilings at considerable expense and is a particular problem in docks and other structures in which posts and pilings are continually subjected to water and weather. While posts and pilings are typically treated chemically, this treatment does not inhibit deterioration to the extent desired.
In the past, various covers or caps for pilings have been suggested or used. These include bituminous material such as tar paper as a cushion on the top of a post, covered with a galvanized metal cap (U.S. Pat. No. 1,637,627), an asphalt covering and a metal cap screwed to the top of the post (U.S. Pat. No. 1,707,397), a steel or copper cover with screws in a flange covering a felt pad over the end of a post, the felt pad serving as a reservoir of preservative (U.S. Pat. No. 1,996,401), a cake of wood preservative on the end of a pole, covered by an elastic cap stretched over the top (U.S. Pat. No. 3,319,328), and a metal pile shoe with wings that fold around the periphery of the post and are nailed in place (U.S. Pat. No. 3,514,959).
The present state of the art to applicant's knowledge includes the use of fiber glass cloth impregnated with a slow cure resin that is layered upon and formed to the contour of the end of a post or piling. This covering tends to pull away during the cure and leaves voids between the post or piling end and the covering cloth and when unsupported and being somewhat brittle in nature, it tends to crack or be otherwise damaged from impacts. The state of the art also includes the use of a soft metal disk across the top of a piling, hammered into shape about the end and nailed in place around a skirt portion. Typically, the formed disk is not in intimate contact throughout its extent with the surface of the post or piling and therefore tends to be easily punctured. In the case of both such covers, substantial preservative is applied prior to covering the post or piling and the application of preservative and installation of either such cover will require substantial time, reportedly on the order of 45 minutes.
In addition to the above, it is known to set poles in the ground and fill the space between the pole and surrounding ground surfaces with an expanded foam resin (U.S. Pat. Nos. 3,403,520 and 3,564,859) or to encase the tip of a pile in concrete (U.S. Pat. No. 4,006,600).
The aforementioned copending application discloses an invention that provides an inexpensive protective end cover for posts and pilings that overcomes disadvantages of the prior art and which is strong and durable as well as easily and quickly applied. The protective cover effectively prevents entrance of moisture to the end of a post or piling and has the advantage of being attractive in appearance and lends itself to bearing indicia or having color significance. A particular embodiment comprises a one-piece preformed (e.g., thermoformed) plastic cap having good impact and abrasion resistance that has a top portion for covering the end of a post and a surrounding skirt portion that extends about a peripheral portion of the post at the covered end. The cap is larger than the end of the post and is secured to and spaced slightly from the end by a foam lining that is formed in place, is semi-rigid, and serves as an adhesive to adhere the cap to the post. The foam not only seals the space between the cap and post against the entrance of moisture, but also expands and fills all voids in the end of the post and between the cap and post. This semi-rigid foam serves as a cushion and provides total support and energy absorption beneath the cap to effectively inhibit puncturing or cracking of the cap from impact.
The cap is secured to a post by mixing foam-forming chemicals and applying them between the end of a post and the cap and allowing the foam to form and expand between the two. The cap is maintained spaced slightly from the post and the expanding foam completely fills any crevices or cracks in the end of the post as well as the space between the post and cap. This assures that the end grain of the post is completely sealed from entry of moisture and provides a complete energy absorbing cushion and support for the cap.
With the thermoformed cap disclosed in the aforementioned application, an inventory of preformed caps is required for poles of various diameter, which is a disadvantage where a large variation in pole size is experienced. Also, caps of the same size, because of their substantially cylindrical skirt portions, do not readily nest and therefore require substantial storage area. In addition, a very substantial investment in thermoforming dies is required to provide the wide range of cap sizes needed, which typically will vary in quarter-inch increments. Also, substantial material is wasted in thermoforming caps because substantial space must be allowed between dies over which a sheet is formed to allow for the thinning of the sheet that occurs. Thus, for many applications a lower cost and more flexible way of providing a satisfactory cap is required.